Photon-counting hexagonal pixel array CdTe detector: Spatial resolution characteristics for image-guided interventional applications.
Photon-counting hexagonal pixel array CdTe detector: Spatial resolution characteristics for image-guided interventional applications.
复制标题
光子计数六边形像素阵列 CdTe 探测器：图像引导介入应用的空间分辨率特性。
DOI：
10.1118/1.4944868
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发表时间：
2016
期刊：
影响因子：
3.8
通讯作者：
Minuti,Massimo
中科院分区：
文献类型：
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作者：
Vedantham,Srinivasan;Shrestha,Suman;Karellas,Andrew;Shi,Linxi;Gounis,MatthewJ;Bellazzini,Ronaldo;Spandre,Gloria;Brez,Alessandro;Minuti,Massimo
目的具有快速成帧能力的高分辨率、光子计数、能量分辨探测器可以同时采集用于减影血管造影术的增强前后图像，没有像素配准伪影，并且可以在图像引导的介入治疗过程中促进高分辨率实时成像。方法利用650μm厚的碲化镉肖特基光子计数探测器同时采集最多两幅能量窗图像，在单能量窗模式下实现10keV或更高能量窗的光子计数。探测器具有六角形像素，其原点为30μm，沿两个正交方向的像素间距分别为60和51.96μm。该探测器在IEC-RQA5光谱条件下进行了表征。该探测器的线性响应范围为与图像引导介入操作相关的空气比释动能率，范围为1.3nGy一帧至91.4nGyGy一帧。使用钨边测试装置确定预取样的调制传递。边缘扩展函数和细采样线扩展函数占六边形采样的比例，由此确定预采样的调制传递函数(MTF)。由于六角形探测器需要重采样到正方形像素以实现无失真显示，通过最小化正方形和六角形像素孔径函数的均方根误差来确定最佳正方形像素尺寸。对于相应的轴，定义为10%MTF的极限分辨率分别为13.3和12周/mm。用三线性插值法对54μm正方形像素进行重采样后，在奈奎斯特频率为9.26μ/mm时的预采样调制传递函数为0.29，沿垂直方向的调制传递函数为0.24，极限分辨率(10%MTF)约为12周期/mm。对条形图图像的视觉分析显示其分辨率接近12线对/mm，对神经血管镍钛合金支架的定性评估显示了在临床相关条件下显示其支柱的能力。结论六角形像素阵列光子计数镉镉探测器在单光子计数模式下提供高空间分辨率。在重采样到最佳正方形像素大小以进行无失真显示后，空间分辨率保持不变。探测器的双能量能力可以实现无伪影减影血管造影术和基础材料分解。所提出的具有能量分辨能力的高分辨率光子计数探测器对于几种图像引导的介入手术以及儿科应用具有重要意义。
PurposeHigh‐resolution, photon‐counting, energy‐resolved detector with fast‐framing capability can facilitate simultaneous acquisition of precontrast and postcontrast images for subtraction angiography without pixel registration artifacts and can facilitate high‐resolution real‐time imaging during image‐guided interventions. Hence, this study was conducted to determine the spatial resolution characteristics of a hexagonal pixel array photon‐counting cadmium telluride (CdTe) detector.MethodsA 650 μm thick CdTe Schottky photon‐counting detector capable of concurrently acquiring up to two energy‐windowed images was operated in a single energy‐window mode to include photons of 10 keV or higher. The detector had hexagonal pixels with apothem of 30 μm resulting in pixel pitch of 60 and 51.96 μm along the two orthogonal directions. The detector was characterized at IEC‐RQA5 spectral conditions. Linear response of the detector was determined over the air kerma rate relevant to image‐guided interventional procedures ranging from 1.3 nGy/frame to 91.4μGy/frame. Presampled modulation transfer was determined using a tungsten edge test device. The edge‐spread function and the finely sampled line spread function accounted for hexagonal sampling, from which the presampled modulation transfer function (MTF) was determined. Since detectors with hexagonal pixels require resampling to square pixels for distortion‐free display, the optimal square pixel size was determined by minimizing the root‐mean‐squared‐error of the aperture functions for the square and hexagonal pixels up to the Nyquist limit.ResultsAt Nyquist frequencies of 8.33 and 9.62 cycles/mm along the apothem and orthogonal to the apothem directions, the modulation factors were 0.397 and 0.228, respectively. For the corresponding axis, the limiting resolution defined as 10% MTF occurred at 13.3 and 12 cycles/mm, respectively. Evaluation of the aperture functions yielded an optimal square pixel size of 54 μm. After resampling to 54 μm square pixels using trilinear interpolation, the presampled MTF at Nyquist frequency of 9.26 cycles/mm was 0.29 and 0.24 along the orthogonal directions and the limiting resolution (10% MTF) occurred at approximately 12 cycles/mm. Visual analysis of a bar pattern image showed the ability to resolve close to 12 line‐pairs/mm and qualitative evaluation of a neurovascular nitinol‐stent showed the ability to visualize its struts at clinically relevant conditions.ConclusionsHexagonal pixel array photon‐counting CdTe detector provides high spatial resolution in single‐photon counting mode. After resampling to optimal square pixel size for distortion‐free display, the spatial resolution is preserved. The dual‐energy capabilities of the detector could allow for artifact‐free subtraction angiography and basis material decomposition. The proposed high‐resolution photon‐counting detector with energy‐resolving capability can be of importance for several image‐guided interventional procedures as well as for pediatric applications.